How to grep for text in a file and display the paragraph that has the text

awkgrepperlsedtext processing

Below is the text in the file:

Pseudo name=Apple
Code=42B
state=fault

Pseudo name=Prance
Code=43B
state=good

I need to grep for "42B" and get the output from the above text like:

Pseudo name=Apple
Code=42B
state=fault

Does anyone have idea on how to achieve this using grep/awk/sed?

Best Answer

With awk

awk -v RS='' '/42B/' file

RS= changes the input record separator from a newline to blank lines. If any field in an record contains /42B/ print the record.

'' (the null string) is a magic value used to represent blank lines according to POSIX:

If RS is null, then records are separated by sequences consisting of a <newline> plus one or more blank lines, leading or trailing blank lines shall not result in empty records at the beginning or end of the input, and a <newline> shall always be a field separator, no matter what the value of FS is.

The output paragraphs will not be separated since the output separator remains a single newline. To ensure that there is a blank line between output paragraphs, set the output record separator to two newlines:

awk -v RS='' -v ORS='\n\n' '/42B/' file

Solution 1

$ echo abc,10.11.13.14,def,1.2.3.4,geh,6.7.54.23 | awk -F, '{for (i=1; i<NF; i+=2) if ($i == "def") print $(i+1)}'
1.2.3.4

In this case, I am looking for a machine name "def", if found, print the next column.

Solution 2

$ echo abc,10.11.13.14,def,1.2.3.4,geh,6.7.54.23 | tr , \\n | awk '/def/ {getline;print}'
1.2.3.4

In this solution, I use the tr command to convert commas to new line, search for "def" and print the line that follows. I hope these solutions work for you.

Grepping for a block of text with parts that can be optional

This would do it i hope. Events go to events file. And messages go to stdout.

Save this file to myprogram.awk (for example):

#!/usr/bin/awk -f

BEGIN {
   s=0;  ### state. Active when parsing inside an event
   nevent=0;  ### Current event number
   printf "" > "events"
}

# Start of event
/^ *Data control raising event/ {
   s=1;
   dentries=0;
   print "*** Event number: " nevent >> "events"
   nevent++
}

# Standard event line
s==1 {
   print >> "events"
}

# DataChangeEntry line
/^ *==== DataChangeEntry/ {
   dentries ++
}

# End of event
s==1 && /^ *\]\]/ {
   s=0;
   print "" >> "events"
   if(dentries==0){
      print "Warning: Event " nevent " has no Data Entries"
   }
}

END {
   print "Total event count: " nevent
}

You can invoke it in different ways:

myprogram.awk inputfile.txt
awk -f myprogram.awk inputfile.txt

Sample output:

Warning: Event 3 has no Data Entries
Total event count: 3

You can check all the events together in the file called events in working directory.

Best Answer

Related Solutions

Grep device name and look for next value :

Solution 1

Solution 2

Grepping for a block of text with parts that can be optional

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